Yes...your clown has black-spot disease. If he's exhibiting normal feeding and breathing behavior (if it doesn't look stressed), then I would suggest doing a regimen of daily fresh-water dips. Here's what I did:
My false percula clown started showing 3-5 spots on its right side of the body. After they started appearing much darker, I decided to catch the clown and do a freshwater dip. Make sure your freshwater is at least the same temperature as your tank water. If you're really accurate, you'd make sure the PH is the same as your tank water as well.
My first dip I left it in there for about 18-20 minutes. Watch the fish carefully for signs of freshwater burn. The clown started looking like it was dying, so I felt badly and let it back into the tank. *BAD* mistake. The next day, it was MUCH harder to catch it with a net.
I made a small temporary housing compartment for my clown with a disposable tupperware container. I punched small holes in the lid so there would be water flow. After its second freshwater dip (took me a while to catch the clown the 2nd time), I had the container ready, and I was able to administer daily freshwater dips for 12-15 minutes each without having to catch the fish each time. The black spots went away within approximately a week.
Hope that helps! Good luck!